JPH01178821A - Electromagnetic flowmeter - Google Patents

Abstract

PURPOSE:To reduce a use amount of platinum, by a method wherein silver paste is applied to a platinum baked part in a partially overlapped state and subsequently again baked to form an electric conductor and an external conductor junction part is directly bonded to the conductor of the silver baked part by soldering. CONSTITUTION:Platinum paste is applied to the surface of an alumina ceramics main body 1 only at a part requiring heat resistance, corrosion resistance and a conductor before baking to form a platinum baked part 2. After the alumina ceramics main body 1 is baked, silver paste is applied to the conductor part between conventional platinum wires and again baked to form the conductor composed of a silver baked part 4. The continuity of the platinum baked part 2 and the silver baked part 4 is performed by applying the silver paste in an overlapped state after baking platinum to again baking the same and penetrating silver particles in the gaps between platinum particles. By this method, the connection of an external conductor 5 can be simply performed by soldering.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to an electromagnetic current meter made of alumina ceramics that uses electrodes to detect electromotive force proportional to the average flow velocity based on electromagnetic induction. Pertains to an electric flow meter with a through body.

[Conventional technology]

Most conventional electromagnetic flowmeters are made of metal, so there is a limit to their use when the fluid being measured is corrosive or at high temperatures. Those made of alumina ceramics are listed as Y1.

However, since the alumina ceramics are electrically insulating, it is important to have a technique for providing a through-hole made of a good electrical conductor on the surface of the alumina ceramic body.

In view of these requirements, in conventional methods, holes are drilled in alumina ceramics before firing, platinum wires for electrodes are inserted into the holes, and shrink-fitted due to the difference in shrinkage during firing, thereby establishing continuity between the platinum wires. The body was made by applying platinum paste to the alumina ceramic surface before firing, and then baking the platinum at the same time as firing.

In addition, in the case of a medium-diameter electromagnetic flowmeter with a slightly larger diameter through which the fluid to be measured passes, a cermet electrode is used because the electrode is large. The method used for firing was to insert it into the alumina ceramic body and heat it by the difference in shrinkage during firing.

(Problem to be solved by the invention) Is the platinum wire for external conductor connection based on the above conventional method?
Since all the m-units including the poles are treated with platinum, the amount of expensive platinum used can be ignored, and it is inevitable that the product cost will be low.

In addition, when bonding the platinum part A to the external conductor wire, the platinum wire is used to connect it by spot welding to ensure continuity with the external sensing element, which not only increases the amount of platinum used, but also slows down the bonding process. This method is complicated and involves problems such as higher manufacturing costs and higher product prices.

[Means for solving problems]

In order to solve the above-mentioned problems, the present invention replaces platinum, which is a replaceable part, with roots to reduce costs, and also develops an electromagnetic flowmeter that can be connected by soldering as an external wire bonding method. did.

That is, as shown in FIG. 1, platinum paste is applied to the surface of the alumina ceramic body (1) before firing only in the areas where heat resistance, corrosion resistance, and ventilation are required to form the platinum baked areas (2).

After firing the alumina ceramic body (1), silver paste is applied to the connecting part between the platinum wires (3) and (3') and baked again to form a conductive body (4).

Conductivity between the platinum baking part (2) and the silver baking part (4) is achieved by baking the platinum, then overcoating with silver paste and baking again, so that the silver particles enter the gaps between the platinum particles.

By the above method, the platinum wire (3') for connecting the external conducting wire (5), which was conventionally necessary in an electromagnetic flowmeter, can be omitted, and the external conducting wire (5) can be easily connected by soldering.

Furthermore, by replacing most of the conductors from platinum to gold, it has become possible to reduce product cost to 10% of conventional products.

In addition, for the medium diameter cermet electrode shown in Figure 3, platinum paste is applied to only the part to be baked and fitted before firing, and after firing, it is inserted into alumina ceramics, and after firing again, platinum paste is applied to the surface of the alumina ceramics. Apply it to the top of the cermet electrode, and then bake it to create a conductor.

[Function and Examples]

The operation and examples of the E6F5 flowmeter of the present invention will be described in detail below, but the content of platinum and silver in the paste used, the baking temperature, the type of solder, the melting temperature, etc. will be explained in detail in this example. Of course, there are no limitations.

The parts that require corrosion resistance and snow resistance, which are characteristics of electromagnetic flowmeters, are shown in Figure 1.Platinum paste is applied on the surface of the alumina ceramic body (1) as before, and the alumina ceramic is fired and G-pull the platinum.

Conductivity between the platinum wires (3) and (3°) is established by applying a silver paste with a silver content of 45-L% to the surface of the alumina ceramics (1) after firing the alumina ceramics (1).
The temperature is raised to 600°C at a rate of increase of 100°C per hour,
After keeping it as it is for 2 hours, it is cooled.

Here, the silver content of the silver paste is preferably 40-t% or more, and the baking temperature is preferably 550 to 850°C.

For silver baking, after providing the conductor (4) using the above method, for platinum baking, coat paste over the part (2) and then bake again to make the silver particles enter into the gaps between the platinum particles. By providing the platinum-printed section (6), the platinum-printed section (2) and the silver-printed section (4) can be ventilated.

After providing the first part using the above method, the external conductor (5) is baked with silver and connected to the conductor (4) using silver-containing solder at the corresponding part at a solder melting temperature of 350°C. .

When using the medium diameter cermet electrode shown in Figure 3,
Apply platinum paste to the part to be shrink-fitted before firing, insert it into alumina ceramics after firing, and after firing again,
A paste is applied to the surface of the alumina ceramics and the top of the cermet electrode, and finally baked to form a W chain.

〔Effect of the invention〕

The electromagnetic flowmeter of the present invention manufactured by the above method significantly reduces the amount of platinum used and reduces the process cost by switching from spot welding to soldering, which is 10% lower than the conventional electromagnetic flowmeter. It can be manufactured at a cost of

[Brief explanation of the drawing]

Fig. 1 shows the electromagnetic flowmeter of the present invention using platinum wire electrodes, Fig. 2 shows its conventional example, and Fig. 3-1
4 shows a case where the cermet electrode of the electromagnetic flowmeter of the present invention is used, and FIG. 4 shows a conventional example thereof. (1) Alumina ceramic body (2) Platinum baking part (3) (3°) Platinum wire (4) Silver baking part (5) External conductor (6) Facing - silver baking part (7) Electrode

Claims (1)

[Claims] In electromagnetic flowmeters in which the fluid to be measured passes through is made of alumina ceramics, etc., platinum paste is applied to the areas that require heat resistance and corrosion resistance on the alumina ceramic surface corresponding to the electrical conductor formation area, and then fired. In order to form an electrical conductor and establish electrical continuity between the platinum baked part and the external conductor, silver paste is partially overcoated on the platinum baked part, and after application, it is rebaked to form an electrical conductor by silver baking. ,
An electromagnetic flowmeter characterized in that an external groove line joint part can be directly soldered to the conductor of the silver baked part.